This invention relates to a cooling water drainage system for a marine propulsion engine and more particularly to a system for purging the engine cooling system of water when engine operation is discontinued.
In many marine applications, the watercraft is powered by a liquid cooled internal combustion engine. Such engines are employed both for inboard, inboard/outboard and outboard drive arrangements. Although closed cooling systems have been proposed for such applications, such closed systems have some disadvantages. Therefore, it is the normal practice with such applications for the coolant to be drawn for the engine from the body of water in which the watercraft is operated and then returned back to that water body after is has been circulated through the engine cooling system. Although such arrangements offer considerable advantages, simplicity being a major one of them, there are some disadvantages.
With watercraft there may be long periods of time when the engine is not being operated. Under these conditions, it is desirable to ensure that the cooling system is purged of water. If water is permitted to remain in the engine cooling system, particularly in salt water environments, corrosion can become a significant problem. In addition, if the temperature becomes low enough, there is always a danger of freezing. There are many instances, however, where the water may remain in at least a portion of the engine cooling jacket once the engine is shut off. This may happen in an inboard application if the engine, as is the normal case, is positioned below the level of water in which the watercraft is operating. Furthermore, with inboard/outboard drive arrangements the water is frequently drawn in through the pivotally supported outboard drive unit of the arrangement. This outboard drive unit is tilted up when the watercraft is not in use and hence coolant may be trapped in the engine cooling jacket under these circumstances. A similar situation can arise with outboard motors.
It is, therefore, a principle object of this invention to provide an improved coolant water system for a marine propulsion engine wherein coolant is purged from the engine cooling jacket when the engine is not being operated.